Endless non-metallic belt for intermittently moving a transducer head transversely across a rotary magnetic disc

ABSTRACT

An intermittent feeding device provides a translation and intermittent feed to a recording and reproducing head used for cooperating with a rotary recording medium. An intermittent rotation driving source, such as a stepping motor, drives a belt intermittently thereby causing the transducer head secured on the belt to make intermittent stepping movements. Vibrations, such as a hunting of the rotary driving source, are absorbed by the belt and not transmitted to the tip of the transducer head.

United States Patent Kinjo et al.

1451 July 31,1973

ENDLESS NON-METALLIC BELT FOR INTERMITTENTLY MOVING A TRANSDUCER HEADTRANSVERSELY ACROSS A ROTARY MAGNETIC DISC Inventors: Hisao Kinjo; FumioAkuwa, both of Yokohama, Japan Assignee: Victor Company of Japan, Ltd.,

Yokohama-City, Japan Filed: Oct. 30, 1970 Appl. No.: 85,463

Foreign Application Priority Data Nov. 1, 1969 Japan 44/87270 Aug. 17,1970 Japan 45/71874 U.S. Cl. 178/6.6 DD, 179/1002 CA Int. Cl. H04m 5/78,G1 1b 21/08 Field of Search 179/1002 T, 100.2 CA,

179/1002 MD; l78/6.6 DD; 340/l74.1 C

[56] References Cited UNITED STATES PATENTS 3,176,083 3/1965 Hauser179/1002 T 3,548,095 12 1970 Poulett l78/6.6 DD 3,291,920 12 1966 Hauser179 1002 T Primary ExaminerBernard Konick Assistant Examiner-Robert S.Tupper AttorneyLouis Bernat [57] ABSTRACT 15 Claims, 13 Drawing Figures1 1 O O J51, J21, 4i 1 3g i: 3': 45-: E 5 42 5/ L".

PAIENIE JUL 1 ma SHEEI 1 0F 5 P FIG. IA m FIG. 2

INVENTORS H/SHO KINJO BY FuM/o HKUWH O iu "can;

PAIENIwJum #915 3.749.827

sum 2 0r 5 III/4- INVENTORS HISHO KINJO BY Fum/o HKUWF) PATENTED 3 1 73SHEET 3 OF 5 FIG. 5

INVENTORS HISFIO KINJO BY FUPHO HKUWF) PAIENIED JUL 3 I ma SHEET l 0F 5FIG. 7

IIW

INVENTORS HISHO K/NJO BY O HKUWH PAIENIEDJUUWB 3.749.827

SHEEY 5 BF 5 INVENTORS H1390 KINJO ENDLESS NON-METALLIC BELT FORINTERMITTENTLY MOVING A TRANSDUCER HEAD TRANSVERSELY ACROSS A ROTARYMAGNETIC DISC This invention relates to an intennittent feeding devicefor transducer heads, and more particularly to a device for providing atranslational and intermittent feed to recording and reproducing headsfor cooperating with a rotarty recording medium.

A magnetic recording and reproducing apparatus uses a rotary magneticmedium such as a rotary magnetic sheet or a rotary magnetic disk. Amagnetic head, for recording on and reproducing from the rotary magneticmedium, generally needs to be moved by a translational feeding motion.In case a recording and a re producing are effected by formingconcentric tracks on the rotary magnetic mdeium, the magnetic head isfed translationally and intermittently. Whereas, in case a recording anda reproducing are effected by forming a spiral track on the rotarymagnetic medium, the magnetic head is fed translationally andcontinuously.

For providing a intermittent feed to the magnetic head, a device isemployed which converts an intermittent rotary movement of theintermittent rotary driving source (such as a pulse motor or a steppingmotor) into an intermittent linear and translational movement. Aconventional magnetic head feeding device has used a mechanismcomprising a feed screw provided on a rotary shaft of a pulse motor. Ahalf nut is threaded on the feed screw. The half nut carries a magnetichead. Another conventional magnetic head feeding device has employed amechanism having a pinion provided on a rotary shaft of a pulse motorand a rack which meshes with the pinion. The rack carries a magnetichead.

In a pulse motor, however,'hunting generally takes place when itsintermittent rotary movement is started. In the aforementionedconventional devices, mechanical vibrations are caused during theintermittent rotary movement of the pulse motor. These vibrations aredirectly transmitted to the tip of the magnetic head. In this case, themagnetic head cannot maintain its normal contact with the rotarymagnetic medium and jitters will take place. Further, the magnetic headmakes contact with the rotary magnetic medium at a position which is outof a normal contact position, whereby mistrackings of the magnetic headon the magnetic medium may occur.

A further conventional magnetic head feeding device has employed a steelbelt fixedly carrying a magnetic head on the upper surface thereof. Thesteel belt is wound at both ends around two driving pulleys. In thisconventional device, the magnetic head carried on the steel belt ismoved by winding the steel belt on one of the rotating driving pulleys.This device has an advantage in that there is no slippage of the belt.On the other hand, however, this device is disadvantageous in that thediameter of the wound steel belt on the driving pulley gradually changesas the steel belt is wound around the driving pulley. Thus, the magnetichead is prevented from effecting an intermittent movement at an equalinterval, and the pitch of the track formed on the rotary magneticmedium gradually changes and cannot be maintained at a constant value.

It is, therefore, a general object of the present invention to provide anovel and useful intermittent feeding device for transducer heads whichcan eliminate the afore-mentioned disadvantages of the conventionaldevices.

Another object of the invention is to provide an intermittent feedingdevice for transducer heads in which mechanical vibrations produced by arotary driving source are not transmitted directly to the transducerheads. Accordingly, an occurrence of jitter in'recording and reproducingsignals can be prevented.

A further object of the invention is to provide a device which iscapable of feeding intermittently a transducer head for forming tracksof equal pitches on a rotary recording medium. Accordingly, a veryaccurate tracking of the transducer head on the recording medium isobtainable in the device according to the invention.

A further object of the invention is to provide a device which iscapable of eliminating a sliding slippage due to overload and an elasticslippage due to the elasticity of a belt, thereby feeding a transducerhead by the belt without slipping.

A still further object of the invention is to provide a transducer headfeeding device in which an intermittent rotary stepping angle of anintermittent rotary driving source in made greater and the diameter of adriving shaft is made larger by the employment of a reduction gear. Bythis arrangement, torque load can be reduced according to a reduction ofgear ratio and also a stepping pitch angle error can be reduced.

These and other objects and features of the invention will becomeapparent from the following description made with reference to theaccompanying drawings, in which:

FIGS. 1A to 1C are graphical diagrams respectively showing driving pulsewave forms, a stepping response characteristic of a pulse motor and itsoscillation phenomenon;

FIG. 2 is a side elevation of an embodiment of a recording andreproducing apparatus using a rotary magnetic disk to which a deviceaccording to this invention is applied;

FIG. 3 is a schematic plan view of a first embodiment of the deviceaccording to the invention;

FIG. 4 is a side elevation view of the device shown in FIG. 3;

FIG. 5 is a plan view of a second embodiment of the device according tothe invention;

FIG. 6 is a side elevation of the device shown in FIG.

FIG. 7 is a schematic plan view of a third embodiment of the deviceaccording to the invention;

FIG. 8 is a side elevation view of the device shown in FIG. 7;

FIG. 9 shows a pattern of tracks formed on the rotary magnetic disk;

FIG. 10 is a schematic plan view of a fourth embodiment of the deviceaccording to the inventiomand FIG. 11 is a side elevation view of thedevice shown in FIG. 10.

Referring now to FIG. 1, a group of driving pulses P having a period of,for example, one-thirtieth seconds as shown in FIG. 1A is applied to apulse motor. The pulse motor generally makes an intermittent rotarymovement with a stepping response characteristic as shown in FIG. 1B.The rotation of the motor builds up within a period of time t, after itsrotation is started. At the end of building-up of the motor rotationthere is, an

overshooting, and a subsequent hunting phenomena occurs. it takes aperiod of time t before the hunting substantially ends. If thisrotational oscillations or vibrations are transmitted directly to amagnetic head, vibrations as shown in FIG. 1C occur at a tip of themagnetic head. The recording or reproducing by the magnetic head mustoccur within the period of onesixtieth seconds (t before the motorstarts its next intermittent rotary movement. At the initial portion ofthis period t the aforementioned hunting has not yet completely ceased.

In the conventional devices as hereinabove described, the magnetic headis obliged to start its recording or reproducing before the hunting hascompletely ceased. In this case, the magnetic head cannot contact therotary magnetic medium under a normal condition. Therefore, mechanicaljitters are produced in recording or reproducing signals. At the sametime, mistrackings of the magnetic head will occur on the rotarymagnetic medium.

In the device according to the invention hereinbelow described, theaforementioned disadvantages of the conventional devices are completelyeliminated.

One embodiment of the recording and reproducing apparatus using a rotarymagnetic disk to which the device according to the invention is appliedwill now be illustrated with reference to FIG. 2. A magnetic disk havingupper and lower magnetic surfaces is rotated by a disk motor 11 at arotation velocity of 60 r.p.s. Pulse motors 12a and 12b supported on themounting table are rotated alternately and intermittently by drivingpulses which are applied to the motors. Belts 13a and 13b areintermittently driven by the pulse motors 12a and 12b. Magnetic heads14a and 14b are secured to the belts 13a and 13b so as to contact themagnetic disk 10.

The magnetic heads 14a and 14b are intermittently and alternatelystepped forward by intermittent rotation of the pulse motors 12a and12b. The magnetic heads 14a and 14b are translationally stepped in aradial direction across the magnetic disk 10. The magnetic heads 14a and14b record and reproduce video signals, of one field unit per concentrictrack, on the magnetic disk 10. Recording or reproduction occurs whilemagnetic heads are in a standstill state.

Each embodiment of the transducer head feeding device including thepulse motor and belt will now be described.

FIGS. 3 and 4 show the first embodiment of the device according to theinvention. A driving shaft 21 is directly driven by a stepping motor 20,with an intermittent stepping rotation. A flat or plane belt 22 isprovided between the driving shaft 21 and a driven shaft 23, the beltforming an endless loop. The belt 22 is made of a material of relativelysmall strain. The outer peripheral surfaces of the driving shaft 21 andthe driven shaft 23 are knurled so as to prevent slipping of the belt22.

A pinch roller 24 is rotatably supported between ends of arms 25. Thearms 25 are pivotally mounted on brackets 26 which rotatably support thedriving shaft 21. Springs 27, provided between the arms 25 and thebrackets 26, cause the pinch roller 24 to press against the belt 22wound around the driving shaft 21. The driven shaft 23 is rotatablysupported between ends of arms 28 which are pivotally mounted onbrackets 29. Springs 30, for providing an initial tension and a backtension to the belt 22, are provided between the arms 28 and a fixedpart of the apparatus. In FIG. 3, the arms 28 receive rotating forces inthe counterclockwise direction from the springs 30, so that the belt 22receives a greater tension.

A head supporting base 31 is secured to the belt 22. A video signalrecording and reproducing magnetic head 32 is mounted on the base 31. Alinear guide bar 33 is provided in parallel with the moving direction ofthe belt 22. A guide 34 formed integrally with the base 31 engages theguide bar 33. As the belt 22 moves, the head 32 is guided by the guidebar 33 and the guide 34.

The driving shaft 21 is rotated intermittently by the intermittentrotation of the stepping motor 20, whereby the belt 22 movestranslationally and intermittently. This causes the magnetic head 32 tomake a translational and intermittent stepping movement. The accuracy ofthe position of tracks formed by the magnetic head 32 on the roatrymagnetic disk depends upon the accuracy of one step of the belt 22. Theaccuracy of the guide bar 33 and the guide 34 determines the accuracy ofthe position of the magnetic head 32, in the rotational tangentialdirection of the magnetic disk, as related with the occurrence ofjitter.

In a power transmission system using a flat belt, there are generallytwo kinds of slippage, namely, a sliding slip and an elastic slip. Inthe power transmission systern of the present embodiment, a greatinitial tension is applied to the belt to prevent the sliding slip dueto an overload. Furthermore, the pinch roller 24 is cuased to pressagainst the belt 22 thereby to hold the belt 22 between the drivingshaft 21 and the pinch roller 24. The sliding slip generally does nottake place unless the belt is overloaded. The aforementionedconstruction of the embodiment is sufficient to prevent occurrence ofsuch sliding slips.

In order to prevent the elastic slip, the belt 22 is made of a materialwhich is flexible, but not elastic, and it has a suitable viscosityresistance and a small strain. In the present embodiment, the belt 22consists of a glass fiber belt body coated with polyurethane resin. Astrain caused by a difference between a tension force on the tight sideof the belt and a tension force on the slack side of the belt is small.The difference between an elongation of the tight side of the belt andan elongation of the slack side of the belt is substantially zero.Accordingly, occurrence of the elastic slip can be avoided.

Furthermore, the driven shaft 23 is energized by the springs 30 to applya constant back tension to the belt 22 in the same direction as thedirection of the initial tension. In other words, the driven shaft 23performs a function of a tension roller. Accordingly, a slippage due tothe elongation of the belt, with lapse of time, can be avoided. Thus, inthe device of the aforementioned construction, the sliding slippage dueto overload and the elastic slippage due to elasticity of the belt areeliminated. Moreover, the vibrations caused by the starting of theintermittent rotation of the stepping motor 20 are effectively damped bythe belt 22 and are not transmitted to the tip of the magnetic head 32.

The second embodiment of the device according to the invention will nowbe described with reference to FIGS. 5 and 6. A stepping motor 40 drivesa driving shaft 42 through a coupling 41 and causes intermittentrotations of the driving shaft 42. The driving shaft 42 is rotatablymounted on a bracket 43 secured to a base 44. A driven shaft 45 isrotatably mounted on a bracket 46 which is mounted on the base 44 so asto pivot slightly about an axis 47. In this embodiment, a rotationalangle for one step of the stepping motor 40 is 1.8", and the diametersof the driving shaft 42 and the driven shaft 45 are 8.0 mm,respectively. A flat or plane belt 48 is provided between the drivingshaft 42 and the driven shaft 45. In this embodiment, the belt 48consists of silicon rubber containing glass fiber cloth. The outerperipheral surfaces of the driving shaft 42 and the driven shaft 45 areknurled so as to prevent a slipping of the belt 48.

The bracket 46 is provided with screws 50 threaded therewith. The screws50 have head portions 51. The ends of the screws 50 always contact aside of a fixed bracket 49. Accordingly, the bracket 46 can be pivotedslightly by turning the head portions 51 of the screws 50, whereby thedistance between the bracket 46 and the bracket 49 can be adjusted.Thus, the distance be tween the driving shaft 42 and the driven shaft 45can be adjusted. By this arrangement, the initial tension applied to thebelt 48 is adjustable so that the difference between an elongation thetight side of the belt and an elongation of the slack side of the beltmay become substantially zero.

Two guide bars 52a and 52b are supported between the brackets 49 and 53in parallel with the belt 48. A head supporting base 54, having guides55a and 55b at opposite ends thereof, is secured to the belt 48. Theguides 55a and 55b are respectively engaged with the guide bars 52a and52b. A head assembly 57, including head tips 56, is mounted on the base54. A screw 58 for adjusting the head tip position is also provided onthe base 54. The weights of the base 54 and the head assembly 57 shouldpreferably be as small as practicably possible. 7

A switch operating cam 59 protrudes from a side of the guide 55a. Asafety limit switch 60 is mounted on the bracket 49. When the headassembly 57 has completed its intermittent movement to the left end inthe figure, the cam 59 pushes an actuator 61 of the switch 60 therebyopening the switch 60. The switch 60 opens the power circuit of thestepping motor 40 so as to stop the "rotation of the motor. A safetylimit switch 62 is mounted on the base 44. When the magnetic headassembly 57 has completed its intermittent movement to the right end inthe figure, the cam 59 pushes anactuator 63 of the switch 62 therebystopping the rotation of the stepping motor 40. A magnet switch 64 isadapted for stopping the magnetic head assembly 57 when it is broughtback to a starting position. When the magnetic head assembly 57 movesleftward, as viewed in the figure, by a quick return motion and hasreached a predetermined recording and reproducing starting postion, amagnet 65 contained in the cam 59 energizes the switch 64, which opensto stop the motor 40.

As in the case of the first embodiment hereinabove described, the belt48 effects its translational and intermittent movement by theintermittent rotation of the stepping motor 40, thereby causing the headtips 56 of the magnetic head assembly 57 to make a stepping movement ina radial direction over the magnetic disk. It is to be noted that, inthis embodiment, there are no members corresponding to the pinch roller24 and the springs 30 used in the aforementioned first embodiment. Thesame accuracy can be achieved, in this embodiment, by turning the screws50 and setting the initial tension of the belt 48 at a predeterminedvalue.

The third embodiment of the device according to the invention will nowbe illustrated with reference to FIGS. 7 and 8. Throughout FIGS. 5 to 8,the same or similar components are designated by the same referencenumerals and the description thereof will be omitted hereafter. A pulsemotor is provided with a small gear 71 on the rotary shaft thereof. Thedriving shaft 42 is provided with a large gear 72 at one end thereof.The gear 71 meshes with the gear 72. The number of teeth of the gear 71is n while the number of the gear 72 is N n). The intermittent rotationof the pulse motor 70 is transmitted by way of the reduction gearmechanism consisting of the gears 71 and 72 to the driving shaft 42thereby moving the belt 48 translationally and intermittently.

In a pulse motor, generally, if an angle of one step corresponding to anapplication of one pulse, is to be made smaller than a certain degree,the number of poles of the motor and the corresponding number of teethof the gear must be increased. In this respect, the construction of themotor is complicated, and a sufficient accuracy of the stepping anglecan be obtained. Accordingly, the stepping angle of pulse motors whichare generally and practicably used is approximately 2 or more.

On the other hand, in case video signals are recorded and reproduced ona rotary magnetic disk, the feed pitch of a magnetic head is made assmall as possible,

and the number of tracks is made as large as possible so that arecording and reproducing capacity of the disk may be increased. Forexample, it is required that the width of feed pitch of the head he onthe order of to 200 p..

In FIG. 9, a part of the track pattern formed on the magnetic disk 10 isshown. Tracks having a width of T' are concentrically formed with guardbands G interpsed therebetween. It is now assumed that the distancebetween centers of adjacent tracks (i.e., track pitch P,) is, forexample, 100 and the diameter of the driving shaft 42 is r mm. If thedriving shaft 42 is directly connected to the rotary shaft of the pulsemotor 70, without employing the reduction gears 71 and 72, the followingformula is obtained.

M360 me where r is the diameter of the driving shaft 42 and 0 is theangle of one step of the pulse motor 40.

From the above formula, r= 360P,/1r 6 If 0 is 2, r (360 X0.l)/(3.l4 X2")5.7 (mm) In the above calculation, thickness of the belt is neglected.

In a practical device, however, it the diameter of the driving shaft 42is reduced to 5.7 mm, the radius of cur accuracy and arrangement of arotor and a stator, elec-' trical irregularity in a driving circuit, andother factors. This pitch angle error does not become greater even ifthe stepping angle of the pulse motor is made larger by applying aplurality of pulses to the motor instead of a single pulse.

Accordingly, the ratio of the pitch angle error, relative todisplacement of the head effected by stepping, becomes small by using aplurality of pulses instead of a single pulse to move the head by onepitch, whereby the accuracy of the tracking is improved. Here, the pitchangle error is designated by A0, and an angle of one intermittent rotarymovement of the pulse motor is designated by 0. If one intermittentrotary movement of the pulse motor causes the magnetic head to make onestep, the intermittent rotational angle is +A6. If two intermittentrotary movements of the pulse motor causes the magnetic head to make onestep, the intermittent rotational angle is ZHAO. Accordingly, a greaternumber of intermittent rotary movements of the pulse motor for onestepping movement of the magnetic head increases the relative accuracyof the stepping position of the magnetic head. It is, therefore, moreadvantageous to use two or three pulses as one unit for driving thepulse motor than to drive it by a single pulse.

This, however, is inconsistent with the aforementioned requirement formaking the diameter of the driving shaft 42 as large as possible. Forexample, if two pulses are used in one unit to feed the head by onepitch the diameter of the driving shaft 42 needs to be slightly lessthan 3 mm. A driving shaft of such a small diameter can not bepractically used.

In the device according to the present embodiment, the reduction gearmechanism consisting of the gears 71 and 72 is used for changing therotational angle and thereby obtaining a drivinG shaft 42 of a preferreddiameter. In this embodiment, the gear ratio of the gear 71 having theteeth number n and the gear 72 having the teeth number N is now selectedas N n 4: l. The pulse motor is normally driven by 4 pulses to cause themagnetic head to make 2 steps and it is driven by 2 pulses to cause themagnetic head to make 1 step when the stepping movement of the magnetichead is reversd. ln this case,

From the above formula, 11' r/360 r x 11.5 mm

Therefore, according to this embodiment, a driving shaft of a largediameter can be used and, at the same time, the stepping pitch angleerror of the pulse motor can be made less than one-half. Furthermore, byvirture of employing the reduction gear mechanism, the load to the pulsemotor shaft is reduced at the same ratio as the reduction gear ratio.Hence, a load torque on the pulse motor shaft is comparitively small,i.e. about one quarter of the conventional device.

The fourth embodiment of the device according to the invention will bedescribed with reference to FIGS. l0 and 11. Throughout FIGS. to 11, thesame or similar components are designated by the same reference numeralsand the description thereofis omitted. A driving shaft 80 having thegear 72, attached thereto is provided with gear portions 810 and 81bspaced apart from each other at a predetermined distance. A driven shaft82 is also provided with gear portions 83a and 83b spaced apart fromeach other at a predetermined distance. Endless timing belts 84a and 84bare respectively provided between the gear portions 81a and 83a andbetween the gear portions 81b and 83b. The head supporting base 54 issecured to the timing belts 84a and 84b.

The timing belts 84a and 84b are respectively formed with involute teethon their inner sides. The gear portions 81a, 81b, 83a and 83b have alsoinvolute teeth which mesh with the teeth of the timing belts 84a and84b. Accordingly, backlash between the timing belt 84a and the gearportions 81a and 83a and between the timing belt 84b and the gearportions 81b and 83b are very small. An accurate driving can beeffected.

According to this embodiment, the application of initial tension to thebelt is not required since the belt is meshed with the driving shaft.Hence an unnecessary load is not applied to the pulse motor 70, wherebya more accurate intermittent stepping movement of the magnetic head isensured.

In the first and second embodiments as previously described, the timingbelt may be used instead of the flat belt. Gear portions which mesh withthe timing belts may be provided on the driving shaft and the drivenshaft respectively.

What we claim is:

1. An intermittent feeding device for a transducer head comprising atransducer head for recording and reproducing on a rotary magneticmedium, an intermittent rotary driving source means for intermittentlymoving said transducer head, a driving shaft connected to said rotarydriving source means, said driving shaft being knurled on its outerperipheral surface and intermittently rotated by said intermittentrotary driving source means, a rotatable driven shaft knurled on itsouter peripheral surface, an endless, flexible, nonmetallic flat beltmeans trained around and extending between said driving shaft and saiddriven shaft, said transducer head being secured to said belt, and guidemeans for guiding said head in a path transverse to the direction ofmovement of said rotary magnetic medium.

2. The device of claim 1 and means for tensioning said belt between thedriving shaft and the driven shaft with a large initial tension so thatthere is substantially no difference in elongation between the tightside and the slack side of the belt.

3. The device of claim 1 which further comprises means for adjusting thedistance between the driven shaft and the driving shaft so as to adjustthe tension applied to the belt.

4. The device of claim 1 which further comprises a pinch roller, saidbelt being wound around the driving shaft and passing between said shaftand pinch roller, and means for energizing the driven shaft in adirection which tightens the belt so as to provide an initial tensionand a back tension to the belt.

5. The device of claim 1 wherein said rotary driving source means is anintermittently rotary motor, said rotary magnetic medium is a rotarymagnetic disk, said belt is a fiber member, and means comprising saidbelt for causing said transducer head to make an intermittent steppingmovement radially across the rotary magnetic disk responsive to anintermittent movement of the belt accompanying an intermittent rotationof the motor.

6. The device of claim 5 which further comprises a first gear mounted onthe rotary shaft of the rotary motor and a second gear mounted on thedriving shaft, said first gear meshing with the second gear, said secondgear having a larger number of teeth than the number of teeth of thefirst gear, and said first and second gears forming a rotary reductiongear mechanism.

7. An intermittent feeding device for transducer heads comprising twotransducer heads for recording and reproducing video signals on a rotarymagnetic medium, a pair of driving means each for intermittently andalternately moving one of said two magnetic heads respectively to form apath, to record every other field of the video signals, each of saiddriving means including a driving shaft, operator means responsive todriving pulses for intermittently rotating said driving shaft over astep of a predetermined angle, a rotatable driven shaft, belt meansextending between said driving shaft and said driven shaft and havingone of the transducer heads secured thereto, said belt being made of aflexible, non-elastic material, guide means for guiding the one of thetransducer heads in a path transverse to the direction of movement ofsaid rotary magnetic medium, said belt being a flat belt, said drivingshaft and said driven shaft being respectively knurled on their outerperipheral surfaces, and means for tensioning said belt wherein saidbelt comprises a glass fiber belt body coated with polyurethane resin.

8. An intermittent feeding device for transducer heads comprising twotranducer heads for recording and reproducing video signals on a rotarymangetic medium, a pair of driving means each for intermittently andalternately moving one of said two magnetic heads respectively to form apath, to record every other field of the video signals, each of saiddriving means including a driving shaft, operator means responsive todriving pulses for intermittently rotating said driving shaft over astep of a predetermined angle, a rotatable driven shaft, belt meansextending between said driving shaft and said driven shaft and havingone of the transducer heads secured thereto, said belt being made of aflexible, non-elastic material, guide means for guiding the one of thetransducer heads in a path transverse to the direction of movement ofsaid rotary magnetic medium, said belt. being a flat belt, said drivingshaft and said driven shaft being respectively knurled on their outerperipheral surfaces, and means for tensioning the belt, wherein saidbelt comprises a combination of silicon rubber and glass fiber cloth.

9. An intermittent feeding device for transducer heads comprising twotransducer heads for recording and reproducing video signals on a rotarymagnetic medium, a pair of driving means each for intermittently andalternately moving one of said two magnetic heads respectively to form apath, to record every other field of the video signals, each of saiddriving means including a driving shaft, operator means responsive todriving pulses for intermittently rotating said driving shaft over astep of a predetermined angle, a rotatable driven shaft, belt meansextending between said driving shaft and said driven shaft and havingone of the transducer heads secured thereto, said belt being made of aflexible, non-elastic material, guide means for guiding the one of thetransducer heads in a path transverse to the direction of movement ofsaid rotary magnetic medium, said belt being a flat belt, said drivingshaft and said driven shaft being respectively knurled on their outerperipheral surfaces, and means for tensioning said belt, wherein saidtensioning means comprises means for adjusting the distance between thedriving shaft and the driven shaft in order to adjust the tension in thebelt.

10. An intermittent feeding device for transducer heads comprising twotransducer heads for recording and reproducing video signals on a rotarymagnetic medium, a pair of driving means each for intermittently andalternately moving one of said two magnetic heads respectively to form apath, to record every other field of the video signals, each of saiddriving means including a driving shaft, operator means responsive todriving pulses for intermittently rotating said driving shaft over astep of a predetermined angle, a rotatable driven shaft, belt meansextending between said driving shaft and said driven shaft and havingone of the transducer heads secured thereto, said belt being made of aflexible, non-elastic material, guide means for guiding the one of thetransducer heads in a path transverse to the direction of movement ofsaid rotary magnetic medium, and means for tensioning the belt, whereinsaid belt is a flat belt, said tensioning means comprises spring meansfor energizing the driven shaft in a direction which tightens the belt,and said driving shaft and said driven shaft having knurled outerperipheral surfaces, the device further comprising a pinch roller forpressing the belt against the driving shaft.

11. An intermittent feeding device for transducer heads comprising twotransducer heads for recording and reproducing video signals on a rotarymagnetic medium, a pair of driving means each for intermittently andaltemately moving one of said two magnetic heads respectively to recordevery other field of the video signals, each of said driving meansincluding a driving shaft, operator means responsive to driving pulsesfor intermittently rotating said driving shaft over a step of apredetermined angle, a rotatable driven shaft, belt means extendingbetween said driving shaft and said driven shaft and having one of thetransducer heads secured thereto, said belt being made of a flexible,nonelastic material, guide means for guiding the one of the transducerheads in a path transverse to the direction of movement of said rotarymagnetic medium, and means for tensioning the belt, wherein said belt isa tim- 'ing belt formed with involute teeth on the inner side,

both said driving shaft and said driven shaft having involute teeth inmeshing engagement with the involute teeth of the timing belt.

12. The device of claim 11 wherein said operator means has a rotaryshaft, a first gear mounted on the rotary shaft, and a second gearmounted on the driving shaft, said first gear meshing with the secondgear, the number of teeth on said second gear being greater than thenumber of teeth on the first gear, and said first and second gearsforming a rotary reduction gear mechanrsm.

13. An intermittent feeding device for a transducer head comprising atransducer head for recording and reproducing signals on a rotarymagnetic medium, a driving shaft, a rotatable driven shaft, an endless,flexible, non-metallic belt trained around and extending between onlythe driving shaft and the driven shaft, said belt having a large initialtension so that therev is substantially no difference in tension betweenthe tight side and the slack side of the belt, said belt having saidtransducer head secured thereto, rotary driving source means forintermittently rotating the driving shaft, and guide means for guidingthe head in a path transverse to the direction of movement of saidrotary magnetic 15. The device of claim 13 which further comprises afirst gear mounted on the rotary shaft of the rotary driving sourcemeans and a second gear mounted on the driving shaft, said first gearmeshing with the second gear, said second gear having a larger number ofteeth than the number of teeth of the first gear, and said first andsecond gears forming a rotary reduction gear mechanism.

1. An intermittent feeding device for a transducer head comprising atransducer head for recording and reproducing on a rotary magneticmedium, an intermittent rotary driving source means for intermittentlymoving said transducer head, a driving shaft connected to said rotarydriving source means, said driving shaft being knurled on its outerperipheral surface and intermittently rotated by said intermittentrotary driving source means, a rotatable driven shaft knurled on itsouter peripheral surface, an endless, flexible, non-metallic flat beltmeans trained around and extending between said driving shaft and saiddriven shaft, said transducer head being secured to said belt, and guidemeans for guiding said head in a path transverse to the direction ofmovement of said rotary magnetic medium.
 2. The device of claim 1 andmeans for tensioning said belt between the driving shaft and the drivenshaft with a large initial tension so that there is substantially nodifference in elongation between the tight side and the slack side ofthe belt.
 3. The device of claim 1 which further comprises means foradjusting the distance between the driven shaft and the driving shaft soas to adjust the tension applied to the belt.
 4. The device of claim 1which further comprises a pinch roller, said belt being wound around thedriving shaft and passing between said shaft and pinch roller, and meansfor energizing the driven shAft in a direction which tightens the beltso as to provide an initial tension and a back tension to the belt. 5.The device of claim 1 wherein said rotary driving source means is anintermittently rotary motor, said rotary magnetic medium is a rotarymagnetic disk, said belt is a fiber member, and means comprising saidbelt for causing said transducer head to make an intermittent steppingmovement radially across the rotary magnetic disk responsive to anintermittent movement of the belt accompanying an intermittent rotationof the motor.
 6. The device of claim 5 which further comprises a firstgear mounted on the rotary shaft of the rotary motor and a second gearmounted on the driving shaft, said first gear meshing with the secondgear, said second gear having a larger number of teeth than the numberof teeth of the first gear, and said first and second gears forming arotary reduction gear mechanism.
 7. An intermittent feeding device fortransducer heads comprising two transducer heads for recording andreproducing video signals on a rotary magnetic medium, a pair of drivingmeans each for intermittently and alternately moving one of said twomagnetic heads respectively to form a path, to record every other fieldof the video signals, each of said driving means including a drivingshaft, operator means responsive to driving pulses for intermittentlyrotating said driving shaft over a step of a predetermined angle, arotatable driven shaft, belt means extending between said driving shaftand said driven shaft and having one of the transducer heads securedthereto, said belt being made of a flexible, non-elastic material, guidemeans for guiding the one of the transducer heads in a path transverseto the direction of movement of said rotary magnetic medium, said beltbeing a flat belt, said driving shaft and said driven shaft beingrespectively knurled on their outer peripheral surfaces, and means fortensioning said belt wherein said belt comprises a glass fiber belt bodycoated with polyurethane resin.
 8. An intermittent feeding device fortransducer heads comprising two tranducer heads for recording andreproducing video signals on a rotary mangetic medium, a pair of drivingmeans each for intermittently and alternately moving one of said twomagnetic heads respectively to form a path, to record every other fieldof the video signals, each of said driving means including a drivingshaft, operator means responsive to driving pulses for intermittentlyrotating said driving shaft over a step of a predetermined angle, arotatable driven shaft, belt means extending between said driving shaftand said driven shaft and having one of the transducer heads securedthereto, said belt being made of a flexible, non-elastic material, guidemeans for guiding the one of the transducer heads in a path transverseto the direction of movement of said rotary magnetic medium, said beltbeing a flat belt, said driving shaft and said driven shaft beingrespectively knurled on their outer peripheral surfaces, and means fortensioning the belt, wherein said belt comprises a combination ofsilicon rubber and glass fiber cloth.
 9. An intermittent feeding devicefor transducer heads comprising two transducer heads for recording andreproducing video signals on a rotary magnetic medium, a pair of drivingmeans each for intermittently and alternately moving one of said twomagnetic heads respectively to form a path, to record every other fieldof the video signals, each of said driving means including a drivingshaft, operator means responsive to driving pulses for intermittentlyrotating said driving shaft over a step of a predetermined angle, arotatable driven shaft, belt means extending between said driving shaftand said driven shaft and having one of the transducer heads securedthereto, said belt being made of a flexible, non-elastic material, guidemeans for guiding the one of the transducer heads in a path transverseto the direction of movement of said rotary magnetic medium, said beltbeing a flat belt, said driving shaft and said driven shaft beingrespectively knurled on their outer peripheral surfaces, and means fortensioning said belt, wherein said tensioning means comprises means foradjusting the distance between the driving shaft and the driven shaft inorder to adjust the tension in the belt.
 10. An intermittent feedingdevice for transducer heads comprising two transducer heads forrecording and reproducing video signals on a rotary magnetic medium, apair of driving means each for intermittently and alternately moving oneof said two magnetic heads respectively to form a path, to record everyother field of the video signals, each of said driving means including adriving shaft, operator means responsive to driving pulses forintermittently rotating said driving shaft over a step of apredetermined angle, a rotatable driven shaft, belt means extendingbetween said driving shaft and said driven shaft and having one of thetransducer heads secured thereto, said belt being made of a flexible,non-elastic material, guide means for guiding the one of the transducerheads in a path transverse to the direction of movement of said rotarymagnetic medium, and means for tensioning the belt, wherein said belt isa flat belt, said tensioning means comprises spring means for energizingthe driven shaft in a direction which tightens the belt, and saiddriving shaft and said driven shaft having knurled outer peripheralsurfaces, the device further comprising a pinch roller for pressing thebelt against the driving shaft.
 11. An intermittent feeding device fortransducer heads comprising two transducer heads for recording andreproducing video signals on a rotary magnetic medium, a pair of drivingmeans each for intermittently and alternately moving one of said twomagnetic heads respectively to record every other field of the videosignals, each of said driving means including a driving shaft, operatormeans responsive to driving pulses for intermittently rotating saiddriving shaft over a step of a predetermined angle, a rotatable drivenshaft, belt means extending between said driving shaft and said drivenshaft and having one of the transducer heads secured thereto, said beltbeing made of a flexible, non-elastic material, guide means for guidingthe one of the transducer heads in a path transverse to the direction ofmovement of said rotary magnetic medium, and means for tensioning thebelt, wherein said belt is a timing belt formed with involute teeth onthe inner side, both said driving shaft and said driven shaft havinginvolute teeth in meshing engagement with the involute teeth of thetiming belt.
 12. The device of claim 11 wherein said operator means hasa rotary shaft, a first gear mounted on the rotary shaft, and a secondgear mounted on the driving shaft, said first gear meshing with thesecond gear, the number of teeth on said second gear being greater thanthe number of teeth on the first gear, and said first and second gearsforming a rotary reduction gear mechanism.
 13. An intermittent feedingdevice for a transducer head comprising a transducer head for recordingand reproducing signals on a rotary magnetic medium, a driving shaft, arotatable driven shaft, an endless, flexible, non-metallic belt trainedaround and extending between only the driving shaft and the drivenshaft, said belt having a large initial tension so that there issubstantially no difference in tension between the tight side and theslack side of the belt, said belt having said transducer head securedthereto, rotary driving source means for intermittently rotating thedriving shaft, and guide means for guiding the head in a path transverseto the direction of movement of said rotary magnetic medium wherein saidbelt is a flat belt, and said driving shaft and said driven shaft arerespectively knurled on their outer peripheral surfaces.
 14. The deviceof claim 13 which further comprises a pinch roller, said belt beingwound Around the driving shaft and passing between said shaft and pinchroller, and means for energizing the driven shaft in a direction whichtightens the belt so as to provide an initial tension and a back tensionto the belt.
 15. The device of claim 13 which further comprises a firstgear mounted on the rotary shaft of the rotary driving source means anda second gear mounted on the driving shaft, said first gear meshing withthe second gear, said second gear having a larger number of teeth thanthe number of teeth of the first gear, and said first and second gearsforming a rotary reduction gear mechanism.